1. Field of the Invention
The present invention is concerned with a device for regulating the flow of fluid in medical apparatus in which there is a valve member having a helical passage for flow of the fluid.
2. Description of the Prior Art
There are many applications in medical equipment in which it is necessary to adjust the flow of fluid. Moreover, the adjusting means usually has to be relatively compact. A typical application is in connection with intravenous feeding in which the fluid from a container designed to hold the intravenous fluid is connected by a tube or other flexible conduit to means for introducing the fluid into the patient. Any means for regulating the flow of such fluid must be very compact and must be capable of quickly adjusting the flow of fluid. It also must be capable of adjusting it in very small increments so that the flow rate is exactly what is desired.
The conventional way of adjusting flow of fluid in such apparatus is through a roller flow control clamp. This is referred to in the Dawe U.S. Pat. No. 4,432,762. The difficulty with this type of arrangement is that it is very difficult to effect accurate adjustment and there is a great tendency for the adjustment to shift once it has been set.
This problem is recognized in the McDonnell U.S. Pat. No. 3,841,354 in which there is a male member in threaded connection with a female member, the threads of the male member being less in height than the depth of the grooves in the female member so that there is a passage between the male and female threads. Furthermore, McDonnell suggests varying the depth of the grooves to provide further adjustment. In such a case, the fluid travels helically in the space between the threads. McDonnell specifically is concerned with an arrangement for adjusting the flow of intravenous fluids. The McDonnell device is, however, of a type which requires relatively slow adjustment and, if one wishes to make a major adjustment of the rate of flow, it is necessary to move the movable valve member through a large number of turns.
Various arrangements have been proposed for metering fluid in which a helical fluid channel is employed. Among such patents are the Duncan et al U.S. Pat. No. 2,105,314. In this patent, the threads of the movable male member slidably engage the wall of the female member so that it is possible to move the male valve member longitudinally to effect quick changes in flow. It is impossible, however, to effect accurate minute adjustments. Furthermore, the rate of change of flow is uniform throughout the movement of the valve member.
The Bryant U.S. Pat. No. 2,323,115 also shows an arrangement in which there is a helical passage and in which, in one modification, the depth of the groove progressively varies from one end to the other. There is no suggestion, however, of varying the pitch of the space to obtain additional variation in change of flow.
Other patents which show helical groove flow regulating devices are the Thornycroft U.S. Pat. No. 982,106, the Maskell et al U.S. Pat. No. 3,091,213, the Blass U.S. Pat. No. 2,752,201, the Kauss U.S. Pat. No. 3,143,145, the Persson U.S. Pat. No. 3,907,249, the Bentley U.S. Pat. No. 3,998,244, the Perkins U.S. Pat. No. 4,044,834, the Waller U.S. Pat. No. 4,044,991, and the Leibinsohn U.S. Pat. No. 4,176,683. While all of these arrangements show the flow regulating device in which there is a helical groove the relative length of which is adjusted, none of them are concerned with extremely compact units and none of them are concerned with varying the pitch to obtain added change in the length of the helical path per unit of longitudinal movement of the flow regulating member.